In one respect, Sunday’s early show at the Bluebird Cafe was par for the course. A pair of country singers, songwriters and friends picked up guitars and shared the tiny stage to trade off on tunes they had written.

There was one huge difference, of course: Those songs included “Crazy,” “Sunday Mornin’ Comin’ Down” and “Funny How Time Slips Away,” because the performers were Willie Nelson and Kris Kristofferson.

The country legends made a rare appearance at the Nashville songwriters’ haven as each received a brand-new honor from the Nashville Songwriters Association International: Kristofferson is the namesake of the association’s new lifetime achievement award, and selected Nelson to be its inaugural recipient.

As the pair took the stage, Kristofferson said Nelson had been his and the “serious songwriters’” hero since he first came to Nashville in 1960s.

“He’s unlike anybody else, because he is one of the best songwriters who ever wrote in any language. He’s absolutely a unique singer who doesn’t sound like anybody else ever…He’s probably the funniest human being I’ve ever known. Sometimes, I try to envision who God might be, and he always comes out looking like Willie.”

“I’m really proud to be giving you this,” he told Nelson. “I’m embarrassed that my face and my name is on it.”

“We can take that right off,” Nelson replied dryly, as the packed house of friends and admirers laughed. “I thought I was coming here tonight to give you an award, so I had a great speech all lined up. It couldn’t match what you just said.”

After their performance, the pair went from swapping songs to cracking each other up with stories on Nelson’s tour bus — parked next to Kristofferson’s behind the Bluebird. Kristofferson remembered Nelson visiting him in Mexico on the set of the 1973 film “Pat Garrett and Billy the Kid,” where Nelson picked up a guitar and made a powerful impression on one of Kristofferson’s co-stars.

“Bob Dylan was so knocked out that he made him keep playing,” Kristofferson said. “I think you played all day there by yourself (laughs), just sitting there on (director) Sam Peckinpah’s floor. Dylan was just amazed. It made me respect Dylan, too. But he’s always been a songwriter’s hero.”

Nelson remembered when Kristofferson first came on the scene in Nashville, as “a shock to a lot of people in the so-called hardcore country tradition.

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“First of all, you got popular in the coffee shops with all the young hippies back in those days, and that was hard to digest in a lot of parts of the country. But as they learned more and more about him, they realized that he’s writing songs about us, ‘Help Me Make It Through The Night.’ It didn’t take them long to realize that this guy was the real deal.”

“I rip him off every chance I get,” Nelson joked. “If he comes up with a good melody, or a good line, look for mine (in) the next song.”

Asked if the pair were able to perform together often enough, Nelson replied. “It’s kind of rare, unfortunately, because we enjoy doing it.”

“I never see anybody else…” added Kristofferson. “But every time we get together, it’s amazing.”